This is pretty funny.  While my wife and I were on vacation we visited her grandparents down in south texas and they had a nurse that comes to visit and take care of her grandfather.  We met her and she said that her name was Conchita, or something along those lines... there was a brief pause and a moment later my wifes grandmother said,"I just call her Maria."  I thought to myself, did you just rename this person?  Do you call all the spanish men Juan too.  Shortly after that I found out that one of her middle names was in fact Maria.   I really thought that my wifes grandmother just called her what she wanted and paid no attention to her name cause she could not pronounce it.   THAT would be a really cross cultural faux pas.